When modern mobile cellular radio networks were introduced into the UK in January 1985, the network providers - Vodafone and Cellnet - were not allowed direct access to the customer, by law.
This was a protection so that the networks would do what they do and both wholesalers and retailers could do what they do best.
Within 15 years, the networks had direct control of end-to-end. Some wholesalers and retailers remain but they have greatly limited places to move within what they can do for the end user.
So I think we are seeing a traditional concentration of power as one sees in ANY market. Over time, the manufacturer/wholesaler/retailer chain expands and contracts.